Cardanol/Tung Oil-Derived Epoxy Thermosets with Tunable Performance

In this study, a biobased epoxy thermoset system was developed using cardanol and tung oil as raw materials. Two distinct epoxy resin precursors (a base epoxidized cardanol, EC for short, and an oligomeric epoxidized cardanol-formaldehyde glycidyl ether, ECFGE for short) were synthesized alongside a tung oil-maleic anhydride (TMA) curing agent. By systematically regulating the stoichiometry of TMA, the cross-linking density of the resulting thermosets was precisely controlled. The ECFGE-TMA system with oligomeric structure exhibited a significantly more densely cross-linked network than the EC-TMA system, resulting in substantially enhanced thermomechanical properties including an elevated storage modulus (up to 2015.5 MPa), higher glass transition temperature (up to 92.6 °C), and superior thermal stability. Dynamic mechanical analysis, thermogravimetric analysis, and tensile tests collectively demonstrated that formaldehyde-assisted chain extension in ECFGE was pivotal for achieving these outstanding comprehensive properties. Furthermore, the epoxy networks exhibited excellent chemical degradability in alkaline ethanol solution, achieving near-complete degradation within 6 h. This research provides a sustainable strategy for developing high-performance biobased epoxy resins with tailorable properties and end-of-life degradability, offering a promising alternative to conventional petroleum-based systems.